Transfer journalist Florian Plettenberg confirmed Porto's interest, describing it as "very concrete" while noting that nothing is advanced or agreed. Barcelona head coach Hansi Flick has said a decision on the 37-year-old's future will wait until the season ends.
Lewandowski himself opened the door to a departure after Sunday's El Clasico against Real Madrid.
"There could be an option in a lower league. I am almost 38, but I feel good physically, so I am considering it."
"I have to consider the possibility that perhaps this is the time to play and enjoy life. Maybe that option will come up and I don't rule it out."
Porto have reportedly already made contact with Lewandowski's camp and presented their project. A one-year deal is understood to be under consideration, though the Pole's current salary level poses a significant challenge for the Portuguese club's budget.
A potential lure is the presence of Polish international teammates in the Porto squad, including Jan Bednarek and Jakub Kiwior, as well as rising winger Oskar Pietuszewski.
Lewandowski has been a consistent performer under Flick this season, scoring 18 goals and contributing four assists in 43 appearances as Barcelona won La Liga. His record at the club stands at 119 goals and 24 assists in 190 games across four seasons.
Juventus and AC Milan are also tracking the situation, as are clubs from MLS and Saudi Arabia. Agent Pini Zahavi is currently in Barcelona as talks with the club over a reduced renewal continue in parallel.
A final call is not expected until the season concludes.